Ever work for an overbearing or toxic boss? Research over the years has shown that abusive managers add insurmountable amounts of stress on employees, greatly decreasing their ability to focus and be productive.

Much worse, all the stress and anxiety that come with fear-based styles of management may take a toll on your heart, according to research.

Swedish researchers at the Stress Institute at Stockholm University studied more than 3,100 men over a 10-year period in typical work settings and found that workers' risks for angina, heart attack, and death rose along with having worked for toxic bosses.

The men in the study, 19 to 70 years of age, had their hearts checked at work between 1992 and 1995. The researchers then matched these men with hospital records for heart disease illness and death up to 2003.

During the follow-up period, there were 74 cases of fatal and nonfatal heart attacks or angina or death from heart disease.

The bosses that were deemed to be the worst increased their employees' heart disease risk by 25 percent. And the problems were found to be cumulative: the longer the employees worked for a bad boss, the worse the effect. People who had worked for a poor boss for more than 4 years had a 64 percent higher risk of heart disease. These negative effects affected everyone, regardless of how much they smoked or drank, or their social status or income level.

The study's lead scientist, Anna Nyberg, said "for all those who work under managers who they perceive behave strangely, or in any way they don't understand, and they feel stressed, the study confirms this develops into a health risk."

4 toxic boss traits that led to serious health risks

The researchers found that employees who had managers with the following four negative traits were 60 percent more likely to have suffered a heart attack or other life-threatening cardiac condition.

1. Managers who were incompetent.

This may be the boss that was promoted too soon or hired carelessly and holds a position that is beyond his capabilities. Worse off, people reporting to him are senior level and have expertise that he lacks. Consequently, researchers found that the less competent employees rated their boss's leadership skills, the higher the risk for heart disease. 

2. Managers who were inconsiderate (uncivil).

As Bob Sutton explains in The Asshole Survival Guide, when bad bosses treat people like crap, it destroys their focus and motivation; people are three times less likely to contribute at a high level. The Swedish researchers recommended interventions such as delegating authority to employees and supporting employees' development as a way of honoring and dignifying their contributions.

3. Managers who were secretive.

The statement, "My boss gives me the information I need," when answered in the negative in the ten-question survey, was most predictive of cardiovascular risk from bad managers. This is indicative of the controlling boss that hoards or withholds information and employees often end up lost and confused. The Swedish researchers recommended interventions such as providing employees with information; giving employees sufficient control and power (ownership) in relation to responsibilities, and including employees in decision-making.

4. Managers who were uncommunicative.

Bosses who don't provide clear and realistic goals and expectations for people's work was another predictor of an increasing risk for heart disease in employees. The interventions recommended for improving communication include setting clear work objectives and providing ongoing and frequent feedback.

In closing, enhancing managers' skills by raising their capacity to do these four things really well "could have important stress-reducing effects on employees and enhance the health at workplaces," said the study's lead scientist, Anna Nyberg.